Conventionally, a cell module in which a plurality of unit cells is stacked on each other with a holder interposed therebetween has been known (see, for example, Patent Literature 1). Patent Literature 1 discloses a cell module including a plurality of so-called laminate-type cells stacked on each other. In the cell module, the cells are restrained by sandwiching a sealing portion formed around a power-generating element housing portion of a cell outer casing through a holder.